A 26-year-old man had suffered from several episodes of right upper-quadrant pain for 6 months. Abdominal ultrasonography showed multiple saccular dilatations of the intrahepatic biliary tract, with hepatolithiasis at the bilateral hepatic lobe. Abdominal computed tomography also revealed saccularly dilated intrahepatic ducts with hepatolithiasis. Communication between saccular dilatations of the intrahepatic biliary tract and normal bile ducts was demonstrated by endoscopic retrograde cholangiopancreatography. Choledochal cyst type V (Caroli's disease) was diagnosed. The patient's 29-year-old sister was also diagnosed with Caroli's disease based on abdominal sonography. An ultrasonography survey was carried out on the family. Reports of Caroli's disease occurring in two siblings are rare in the literature.